I have also been prescribed phentermine and prozac. I took phen by itself the first few days because I've heard about the weird side effects you can have with both of them, and lost 3 lbs. Then I started taking it with the prozac and I was just maintaining my weight...so of course I stopped taking them together. Although it did help me control my hungry threw the whole day together. I don't know though, I only took the Prozac for like 3 days...If you do starting taking them together, let me know how it turns out 4 ya! GoodLuck!!